The invention relates to a method for detecting the state of an elevator cage and to an elevator system in which the method is used.
Means are usually present in elevator installations which make it possible to detect the instantaneous position and/or the speed and/or the acceleration of an elevator cage.
There are approaches in which, for example, markings or the like are provided at a guide rail in the elevator shaft and can be scanned from the elevator cage. Other elevator systems have a special elongate apertured strip which is mounted near the elevator cage in the elevator shaft and can be scanned by the elevator cage.
Moreover, it has already been proposed to provide a supporting/drive means (support cable, support belt) with markings and to scan these markings. An example can be inferred from the patent publication WO 2004/106209 A. According to this publication a detector is disposed at a fixed reference point in the shaft, while the supporting/drive means with the markings runs past the detector. In order to avoid problems with oscillations of the supporting/drive means, the detector is fixed in the region of the drive pulley of the drive unit.
The above-described solution has the disadvantage that it comprises a detector mounted in the region of the drive unit of an elevator without an engine room. On the one hand this detector is poorly accessible for elimination of faults and/or for maintenance operations and on the other hand interference fields, which impair the functional reliability of the detector, are present in the region of a modern drive unit supplied by a frequency converter.